Switch-mode power supplies (SMPSs) (“power converters”) are widely utilized in consumer, industrial and medical applications to provide well-regulated power while maintaining high power processing efficiency, tight-output voltage regulation, and reduced conducted and radiated electromagnetic interference (EMI).
To meet these conflicting goals, state-of-the-art power converters (flyback converters, forward converters, boost converters, buck converters, and so on) commonly utilize quasi-resonant control methods. Quasi-resonant control methods induce a resonant waveform having sinusoidal voltage oscillations at the drains of one or more semiconductor switches of the power converter. Through well-timed control actions, the semiconductor switches are turned on at the instants where the drain voltage is minimum (i.e., valley switching), thus minimizing the semiconductor switching losses and drain-source dv/dt slope, leading to increased power processing efficiency and reduced electromagnetic interference (EMI).
Power converters often include a primary side circuit that receives an input voltage and a secondary side that outputs an output voltage that is generated using the input voltage. The primary side circuit is often coupled to the secondary side circuit by a transformer. The output voltage is typically generated using a primary side switch to control a flow of current through a primary winding of the transformer. A synchronous rectifier switch on the secondary side controls a flow of an output current. The synchronous rectifier switch is often implemented as a diode. However, diodes create power losses because of a voltage drop across the diode required to forward bias the diode. In some implementations, the diode is replaced by an actively controlled switch.